Presentation on theme: "1 Secondary 4 Chemistry Extraction of Aluminium via electrolysis JT 2009 Raffles Programme."— Presentation transcript:
1 Secondary 4 Chemistry Extraction of Aluminium via electrolysis JT 2009 Raffles Programme
2 Bauxite is mined Extraction of Aluminium purified by treating with NaOH (Al 2 O 3 is amphoteric and reacts with NaOH) High m.p. : 2045 o C Used as the electrolyte aluminium Bauxite comprises: Al 2 O 3 - aluminium oxide Fe 2 O 3 - iron(III) oxide SiO 2 - silicon dioxide Na 3 AlF 6, cryolite is added to lower the m.p. to 950 o C (this means a great cost reduction!) Al 2 O 3 - aluminium oxide (or alumina)
3 Electrolysis 3. electrolyte: Al 2 O 3 dissolved in cryolite 4. steel tank Overall equation: 4Al 3+ (l) + 6O 2- (l) 4Al(l) + 3O 2 (g) 1. anode: carbon oxidation occurs: 2O 2- (l) O 2 (g) + 4e cathode: carbon reduction occurs: Al 3+ (l) + 3e - Al(l) - 5. molten aluminium is extracted Al 3+ O 2- Al 3+ O 2- (play video)
4 At the anode: -oxygen is produced -the oxygen reacts with the anode, which are at high temperature to produce carbon dioxide -the anode has to be periodically replaced + anode reaction: 2O 2- (l) O 2 (g) + 4e -
5 Uses of Aluminium high tension electric cables (its low density is an advantage) cookware e.g. pots, pans, utensils aluminium foil (play video) construction of aircraft, lightweight vehicles, and ladders (alloy - duralumin* used for aircraft) window frames * Duralumin: aluminium (94%), copper (4%) and magnesium (1%).